The Annoyance Filter.pdf - Fourmilab

58 QUOTED-PRINTABLE MIME DECODER ANNOYANCE-FILTER §61
61. Return the next character from the encoded input stream. Since end of line sequences have been
stripped, we append our own new-line character to the end of each line. This indicates that in the
absence of a soft line break (trailing equal sign), we should emit a line break to the output stream.
〈 Class implementations 11 〉 +≡
int quotedPrintableMIMEdecoder ::getNextChar (void)
{
while (true ) {
if (atEndOfLine ) {
atEndOfLine = false ;
return ’\n’;
}
if (ip < inputLine .length ( )) {
if (ip ≡ (inputLine .length ( ) − 1)) {
atEndOfLine = true ;
}
return inputLine [ip ++];
}
if (¬getNextEncodedLine ( )) {
break;
}
if (inputLine .length ( ) ≡ 0) {
atEndOfLine = true ;
}
}
return −1;
}
62. There are lots of ways of defining “ASCII white space,” but RFC 1521 explicitly states that only
ASCII space and horizontal tab characters are deemed white space for the purposes of Quoted-Printable
encoding. However, we must also cope with POP3 messages where the lines are terminated with CR/LF,
so we extend the definition to allow a carriage return before the line feed. This is easily accomplished
by broadening the definition of white space to include carriage return.
〈 Character is white space 62 〉 ≡
((ch1 ≡ ’␣’) ∨ (ch1 ≡ ’\t’) ∨ (ch1 ≡ ’\r’))
This code is cited in section 256.
This code is used in section 63.